1. Field of Invention
The present invention relates to control of phased array antennas having a small number of elements for radiating and receiving communication signals.
2. Description of the Prior Art
Multi-element phased array antennas for radar systems having hundreds and even thousands of radiating or receiving elements have been extensively used. The technology regarding such phased-array antennas having large numbers of elements is well developed and described in available technical literature.
However, due to certain inherent size limitations in spacecraft, a need has recently arisen for phased-array antennas having a relatively small number of antenna elements, typically from 5 to 17 or so. With such a limited number of antenna elements, design concepts underlying the multi-element radar phased array antennas have to a great extent proven unfeasible.
For example, with such a limited number of elements, the number of steering angles available, as well as steering losses at these angles has often been a critical design problem. Further, steering between various beam angles caused large phase transients in communication signals passing through the antennas with a limited number of elements -- a particularly important consideration when phase modulation signals were used, with phase-locked loops for tracking and synchronization.